.TH IOSTAT 1M 
.SH NAME
iostat \- report I/O statistics
.SH SYNOPSIS
.B iostat
[ option ] ...
[ interval [ count ] ]
.SH DESCRIPTION
.I Iostat
delves into the system and reports certain statistics kept about
input-output activity.
Information is kept about up to three different disks
(RF, RK, RP) and about typewriters.
For each disk, IO completions and number of words transferred
are counted; for typewriters collectively, the number
of input and output characters are counted.
Also, each sixtieth of a second,
the state of each disk is examined
and a tally is made if the disk is active.
The tally goes into
one of four categories, depending on whether the system is
executing in user mode, in `nice' (background)
user mode, in system mode, or idle.
From all these numbers and from the known transfer rates
of the devices it is possible to determine
information such as the degree of IO overlap
and average seek times for each device.
.PP
The optional
.I interval
argument causes
.I iostat
to report once each
.I interval
seconds.
The first report is for  all time since a reboot and each
subsequent report is for the last interval only.
.PP
The optional
.I count
argument restricts the number of reports.
.PP
With no option argument
.I iostat
reports for each disk the number of transfers per minute,
the milliseconds
per average seek,
and the milliseconds per data transfer exclusive of seek time.
It also gives the percentage of time the system has
spend in each of the four categories mentioned above.
.PP
The following options are available:
.TP
.B \-t
Report the number of characters of terminal IO per second as well.
.TP
.B \-i
Report the percentage of time spend in each
of the four categories mentioned above,
the percentage of time each disk was active (seeking or transferring),
the percentage of time any disk was active,
and the percentage of time spent in `IO wait:'
idle, but with a disk active.
.TP
.B \-s
Report the raw timing information: 32 numbers indicating
the percentage of time spent in each of the possible
configurations of 4 system states and 8 IO states
(3 disks each active or not).
.TP
.B \-b
Report on the usage of IO buffers.
.SH FILES
/dev/mem, /unix
